As the core equipment of oil fields, workover rigs are still mainly driven by diesel engines. However, this has led to high energy consumption, high pollution and high noise, which contradicts with our “dual carbon” goal. Therefore, the electrification and upgrading of workover rigs has become the main trend of future kinetic energy conversion.
A preliminary attempt at electrification first turned to grid-power. Taking a 70t grid-powered workover rig as an example, the total power of its motor is 240kW, while the wellhead transformer is generally 50kVA or 75kVA, which cannot meet the power requirements and needs to be equipped with a 200kVA transformer. This has increased costs and also brought safety risks, thus seriously restricted the promotion and application of grid-powered workover rigs. To solve this problem, the customer added a battery energy storage device on the basis of the original grid-powered workover rig to expand capacity and compensate for power. By rationally utilizing the complementarity of grid power and electric energy storage devices, multiple working modes such as independent power supply, grid power supply, and joint power supply are realized. This not only improves power supply reliability, but also effectively reduces energy consumption and pollution, perfectly meeting the requirements of the “dual carbon” goals.
When the workover rig is operating, each oil pipe must be connected or unloaded. Each process of connecting or unloading the oil pipe forms a workover operation cycle. This operation mode obviously presents the characteristics of intermittent cycle. The working conditions of the workover rig are mainly divided into four parts: lifting, shackle, pipe laying and lowering. The power demand curve of each working condition is shown in the figure below:
Using the battery power compensation system to compensate the power of the workover rig, the electric energy storage workover rig adopts DC bus voltage control technology to work in parallel with the wellhead transformer. The energy generated by the grid power and the battery pack in parallel can fully meet the power requirements of the workover operation, and the operating efficiency is better than that of the traditional workover rig.
When a great power is required during the lifting operation, the PCS module of the grid power and the DCDC module of the battery pack will simultaneously power the variable frequency motor to ensure that the motor has sufficient power to meet the needs of large power lift. During the shackle operation, the required power supply is relatively small. At this time, the PCS module of the grid power will independently power the motor, and automatically charge the battery pack through the DCDC module with the excess power in the grid power. This intelligent power management method ensures the full utilization of power. During the lowering operation, the required power supply is also small. At this time, the excess power in the grid power is used to charge the battery pack through the PCS module and the DCDC module. In addition, the potential energy generated during the lowering transforms the motor into a generator, and this part of the potential energy can also be converted into power for the battery pack through the DCDC module.
Project name: Liaoning Panjin Oilfield Workover Rig 60kW/194.5kWh Energy Storage System
Products supplied: 60kW PCS*1, 60kW DCDC*4, EMS*1
Project features: Dynamic capacity expansion, maximum 2C discharge rate
The new electric energy storage workover rig adopts the “grid + multi-drive + DC energy storage” method during operation, and achieves dynamic capacity expansion through the energy storage system to make up for the insufficient capacity and power of the well site transformer.
The PCS and DCDC modules developed by YUNT Energy boast the characteristics of fast response speed, strong overload capacity, and strong grid adaptability. They are matched with high discharge rate batteries, and the maximum discharge rate of the energy storage system can be 2C. The workover rig winch motor has the characteristics of large starting current and strong impact. The strong overload capacity of the PCS and DCDC modules makes the energy storage system perfectly match the on-site application.
The coordinated use of energy storage batteries and grid power has been achieved in this project, which can not only make full use of the power distribution resources at the well site, realize multi-mode power supply and meet the needs of well repair operations, but also reduce the impact of battery charging and discharging on the power grid, thereby playing an active protective role for the grid power.
